This is a resubmission of a competing continuation of a five year project which assessed cognitive deterioration in adolescents with insulin dependent diabetes mellitus (IDDM) during experimentally induced mild hypoglycemia, assessed the relationship between CBF (cerebral blood flow), prior glycemic control and hormonal counter-regulation to degree of cognitive impairment. The current submission seeks to extend this work to Aunderstand the mechanism that causes many children with IDDM to exhibit cognitive deterioration during mild hypoglycemia, and to assess a possible therapeutic strategy to prevent this from happening.@ Investigators seek to Aunravel the effects of the glycemic plateau and to verify the experimental insulin-glucose paradigms used to assess responses to hypoglycemia.